Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method for performing a heat treatment for a predetermined time period and then performing a cooling treatment on thin plate-like precision electronic substrates such as semiconductor wafers, glass substrates for liquid crystal displays, and the like (hereinafter referred to simply as “substrates”) which are sequentially loaded into the substrate processing apparatus.
Description of the Background Art
As well known, products of semiconductor devices, liquid crystal displays, and the like are manufactured by performing a series of processes including cleaning, resist coating, exposure, development, etching, interlayer insulating film formation, heat treatment, dicing, and the like on the aforementioned substrates. A substrate processing apparatus which incorporates a plurality of processing units for performing, for example, a resist coating process, a development process, and heat treatments accompanying these processes among the aforementioned processes and uses a transfer robot to circularly transfer a substrate between the processing units, to thereby perform a series of photolithography processes on the substrate is widely used as a so-called coater-and-developer.
Such a substrate processing apparatus transfers a substrate sequentially to a plurality of processing units and performs a predetermined processings thereon, in accordance with a predetermined processing flow. In performing the processings, when processing times for the processes are different, the process needing the longest processing time determines the overall rate and there occurs retention of substrates (waiting for unloading) in the processing units other than the one which performs the process needing the longest processing time. If the previous process of the process needing the longest processing time is a heat treatment, the substrate stays in a heating unit. When the substrate stays in the heating unit, the substrate is heated for over a specified processing time (overbaked) and this causes a problem of bringing significant hindrance to the processing result.
In recent photolithography processes, particularly, using a chemically amplified resist adaptable to a KrF excimer laser or an ArF excimer laser has become dominant. In a case where the chemically amplified resist is used, since the exposure intensity of the excimer laser is low, a post-exposure bake process is performed on a substrate after exposure and a chain reaction of a resist resin is caused to proceed with a product (acid) which is generated in a resist film by photochemical reaction during exposure as a catalyst. In such a post-exposure bake process, when overbaking occurs, the linewidth uniformity of patterns after development is significantly deteriorated.
In order to prevent such overbaking, it is thought to be effective to configure the processing units in the apparatus or define a processing flow so that a heating unit (e.g., post-exposure baking unit) which does not allow overbaking can take the longest processing time. With such a measure, since there are many empty (available) units, for example, for performing a cooling treatment which is a subsequent process of the post-exposure bake process, it is possible to prevent the retention of the substrate in the post-exposure baking unit.
Further, Japanese Patent Application Laid Open Gazette No. 2004-319626 and Japanese Patent Application Laid Open Gazette No. 6-151293 disclose techniques for preventing overbaking by providing a dedicated mechanism for immediately cooling the substrate after the heat treatment. By providing such a dedicated cooling mechanism, it is possible to reliably prevent overbaking regardless of respective processing times in various processes or a processing flow.
The measure to cause the heating unit which does not allow overbaking to take the longest processing time, however, suppresses an increase in the throughput of the whole apparatus. Further, if there arises a trouble in the downstream of the heating unit in a processing flow, it is impossible to prevent the retention of the substrate in the heating unit and it becomes hard to completely prevent overbaking.
On the other hand, if a dedicated cooling mechanism is provided in a one-to-one correspondence with the heating unit which does not allow overbaking, even when there arises a trouble in the downstream of the heating unit in a processing flow, it is possible to prevent overbaking since the substrate after the heat treatment can be cooled by using the dedicated cooling mechanism. Providing dedicated cooling mechanisms in such a manner, however, causes problems of increasing the size of the apparatus and increasing the manufacturing cost for the apparatus.